Considering compression of solid grain and pore fluids,viscous-coupling interactions and inertial force of fluids,dynamic governing equations for unsaturated soils are established by adopting an exact constitutive for...Considering compression of solid grain and pore fluids,viscous-coupling interactions and inertial force of fluids,dynamic governing equations for unsaturated soils are established by adopting an exact constitutive formula of saturation.These equations are highly versatile and completely compatible with Biot's wave equations for the special case of fully saturated soils.The governing equations in Cartesian coordinates are firstly transformed into a group of state differential equations by introducing the state vector.Then the transfer matrix for layered media are derived by means of a double Fourier transform.Using the transfer matrix followed by boundary and continuity conditions between strata,solutions of steady-state dynamic response for multi-layered unsaturated soils are obtained.Numerical examples show that the echoes generated by boundary and stratum interfaces make the displacement amplitude of the ground surface fluctuate with distance;the relative position of soft and hard strata has a significant influence on displacement.展开更多
The transformation groups and symmetries of the baroclinic mode for rotating stratified flow can be obtained via the standard approach. Applying the symmetry group on some special solutions, the newly obtained results...The transformation groups and symmetries of the baroclinic mode for rotating stratified flow can be obtained via the standard approach. Applying the symmetry group on some special solutions, the newly obtained results disprove a known conjecture.展开更多
The torsional oscillation characteristics on the bending and torsioh coupled vibration of rotary shaft system were investigated using the elasto-dynamic theory and other mathematic methods, such as difference approach...The torsional oscillation characteristics on the bending and torsioh coupled vibration of rotary shaft system were investigated using the elasto-dynamic theory and other mathematic methods, such as difference approach, Fourier transform, and wavelet transform. It is concluded that mass eccentricity and other exciting modalities affect the bending and torsion coupled vibration of rotary shafts. Torsional vibration caused by bending vibration features linearity along with the change of amplitude of bending vibration. Meanwhile, energy spectrum concentrates on high frequency area with the wavelet analysis.展开更多
The delta-sigma converter is one of the high speed and resolution analog-to-digital modulators. Its implementation needs the low oversampling technique and the multi-bit D/A converter. The noise induced by the multi-b...The delta-sigma converter is one of the high speed and resolution analog-to-digital modulators. Its implementation needs the low oversampling technique and the multi-bit D/A converter. The noise induced by the multi-bit D/A converter becomes one of the key factors deteriorating the signal-to-noise rate of the delta-sigma A/D converter. A novel structure with signal unity transfunction, dynamic element matching(DEM) and noise-shaping is discussed. The method is investigated to design converter based on the proposed structure. The behavior simulation indicates that the structure and the design method are feasible.展开更多
The theoretical formulations of Coulomb and Rankine still remain as the fundamental approaches to the analysis of most gravity-type retaining wall,with the assumption that sufficient lateral yield will occur to mobili...The theoretical formulations of Coulomb and Rankine still remain as the fundamental approaches to the analysis of most gravity-type retaining wall,with the assumption that sufficient lateral yield will occur to mobilize fully limited conditions behind the wall.The effects of the magnitude of wall movements and different wall-movement modes are not taken into consideration.The disturbance of backfill is considered to be related to the wall movement under translation mode.On the basis of disturbed state concept(DSC),a general disturbance function was proposed which ranged from-1 to 1.The disturbance variables could be determined from the measured wall movements.A novel approach that related to disturbed degree and the mobilized internal frictional angle of the backfill was also derived.A calculation method benefited from Rankine's theory and the proposed approach was established to predict the magnitude and distribution of earth pressure from the cohesionless backfill under translation mode.The predicted results,including the magnitude and distribution of earth pressure,show good agreement with those of the model test and the finite element method.In addition,the disturbance parameter b was also discussed.展开更多
In order to imitate skin characteristics, a dielectric elastomer (DE) membrane coated with flexible electrodes is applied with high voltage, which can lead to wrinkles and other phenomena. To develop soft-actuated air...In order to imitate skin characteristics, a dielectric elastomer (DE) membrane coated with flexible electrodes is applied with high voltage, which can lead to wrinkles and other phenomena. To develop soft-actuated air vehicles and other equipment, lightweight gas is pumped into a DE spherical shell to generate controllable flight movements. According to experimental phenomena and data, the calculation models of phase transitions on circular DE films are built. Meanwhile, the deformation characteristics of different DE (acrylic polymer and rubber) spherical actuators combined with helium are compared. The peak pressure inside a rubber balloon is greater than that of a VHB (acrylic polymer) balloon shell, but the limit stretch of rubber is much smaller. By taking advantages of this phenomenon, large deformations of a VHB spherical shell can be realized at an actuated state. Moreover, multi-layer spherical DE shells can achieve larger voltage-induced volume change than monolayer ones. The research indicates that pre-stretching is one of the key factors to induce phase transitions between flat, wrinkled and bulging regions on circular DE films, and the internal pressure determines the electromechanical performance of balloon actuators.展开更多
基金National Natural Science Foundation of China(No.10272046)
文摘Considering compression of solid grain and pore fluids,viscous-coupling interactions and inertial force of fluids,dynamic governing equations for unsaturated soils are established by adopting an exact constitutive formula of saturation.These equations are highly versatile and completely compatible with Biot's wave equations for the special case of fully saturated soils.The governing equations in Cartesian coordinates are firstly transformed into a group of state differential equations by introducing the state vector.Then the transfer matrix for layered media are derived by means of a double Fourier transform.Using the transfer matrix followed by boundary and continuity conditions between strata,solutions of steady-state dynamic response for multi-layered unsaturated soils are obtained.Numerical examples show that the echoes generated by boundary and stratum interfaces make the displacement amplitude of the ground surface fluctuate with distance;the relative position of soft and hard strata has a significant influence on displacement.
基金Supported by National Natural Science Foundation of China under Grant Nos.10735030,10675065,and 90503006PCSIRT (IRT0734)+1 种基金the National Basic Research Programme of China under Grant Nos.2007CB814800K.C.Wong Magna Fund in Ningbo University
文摘The transformation groups and symmetries of the baroclinic mode for rotating stratified flow can be obtained via the standard approach. Applying the symmetry group on some special solutions, the newly obtained results disprove a known conjecture.
基金SUPPORTED BY NATIONAL NATURAL SCIENCE FOUNDATION OF CHINA( NO. 50475112)NATURAL SCIENCE FOUNDATION OF TIANJIN (NO. 043601411).
文摘The torsional oscillation characteristics on the bending and torsioh coupled vibration of rotary shaft system were investigated using the elasto-dynamic theory and other mathematic methods, such as difference approach, Fourier transform, and wavelet transform. It is concluded that mass eccentricity and other exciting modalities affect the bending and torsion coupled vibration of rotary shafts. Torsional vibration caused by bending vibration features linearity along with the change of amplitude of bending vibration. Meanwhile, energy spectrum concentrates on high frequency area with the wavelet analysis.
基金National Natural Science Foundation of China(50677014)Doctoral Special Found of Ministry of Education(20060532016)+2 种基金Natural Science Foundation of Hunan Province(06JJ2024)Program for New CenturyExcellent Talents in University(NCET-04-0767)Found of Hunan Education depart ment(05C141)
文摘The delta-sigma converter is one of the high speed and resolution analog-to-digital modulators. Its implementation needs the low oversampling technique and the multi-bit D/A converter. The noise induced by the multi-bit D/A converter becomes one of the key factors deteriorating the signal-to-noise rate of the delta-sigma A/D converter. A novel structure with signal unity transfunction, dynamic element matching(DEM) and noise-shaping is discussed. The method is investigated to design converter based on the proposed structure. The behavior simulation indicates that the structure and the design method are feasible.
基金Project(50678158) supported by the National Natural Science Foundation of China
文摘The theoretical formulations of Coulomb and Rankine still remain as the fundamental approaches to the analysis of most gravity-type retaining wall,with the assumption that sufficient lateral yield will occur to mobilize fully limited conditions behind the wall.The effects of the magnitude of wall movements and different wall-movement modes are not taken into consideration.The disturbance of backfill is considered to be related to the wall movement under translation mode.On the basis of disturbed state concept(DSC),a general disturbance function was proposed which ranged from-1 to 1.The disturbance variables could be determined from the measured wall movements.A novel approach that related to disturbed degree and the mobilized internal frictional angle of the backfill was also derived.A calculation method benefited from Rankine's theory and the proposed approach was established to predict the magnitude and distribution of earth pressure from the cohesionless backfill under translation mode.The predicted results,including the magnitude and distribution of earth pressure,show good agreement with those of the model test and the finite element method.In addition,the disturbance parameter b was also discussed.
基金The National Natural Science Foundation of China(No.51775108)
文摘In order to imitate skin characteristics, a dielectric elastomer (DE) membrane coated with flexible electrodes is applied with high voltage, which can lead to wrinkles and other phenomena. To develop soft-actuated air vehicles and other equipment, lightweight gas is pumped into a DE spherical shell to generate controllable flight movements. According to experimental phenomena and data, the calculation models of phase transitions on circular DE films are built. Meanwhile, the deformation characteristics of different DE (acrylic polymer and rubber) spherical actuators combined with helium are compared. The peak pressure inside a rubber balloon is greater than that of a VHB (acrylic polymer) balloon shell, but the limit stretch of rubber is much smaller. By taking advantages of this phenomenon, large deformations of a VHB spherical shell can be realized at an actuated state. Moreover, multi-layer spherical DE shells can achieve larger voltage-induced volume change than monolayer ones. The research indicates that pre-stretching is one of the key factors to induce phase transitions between flat, wrinkled and bulging regions on circular DE films, and the internal pressure determines the electromechanical performance of balloon actuators.
